21 days of discovery

Inside the chicken:

PresenterPresentation NotesWhich came first: the chicken or the egg? This is a silly riddle, and fun to think about, but today we’re going to start with the chicken. This is a mother hen. Inside her body, an egg begins to form. At first it is mostly “yolk,” and if the egg is a fertile one, an embryo, or baby chicken, will be attached to the yolk. As it passes through this tube, it is coated with albumin, also known as the “white” of the egg. Right before it is laid, it stops in a little compartment where it is coated with a hard covering—the shell actually comes last! This is a continuous process, as one egg is leaving the hen’s body, the next is already well under way.

Inside the egg:

Albumen (egg white)

Germinal disk (baby chick)

Shell

Air cell

Two membranes

ChalazaYolk

PresenterPresentation NotesThe egg contains everything a developing chick (or embryo) needs to grow into a baby chick that can survive in the outside world. The shell is the hard covering that protects the chick, but it also has thousands of tiny holes, called pores, that let oxygen in so that the chick can get new air. The yolk supplies the chick with nutrients. The albumen, or egg white, provides a safe cushion for the chick in case the egg is bumped and also supplies protein when the chick begins to grow very rapidly. The germinal disk is where you can find the chick embryo—it starts out as one tiny cell, but given the right circumstances, it will grow into a full size chicken! The air cell is a pocket of air at the base of the egg that will be used by the chick when it is ready to take its first breath. Chalaza may be a difficult word to say, but it serves an important role by anchoring the yolk in place. This keeps the embryo from getting beat up and bruised as the egg is turned and also keeps it in a place where temperature, moisture, and nutrient access are perfect. Lastly, two membranes can be found just inside the shell. These membranes are like the police of the egg. They make sure that good things like oxygen get in and keep bad things like bacteria stay out. They also ensure that moisture stays inside the egg but waste gasses like carbon dioxide can get out.

Outside the egg:

PresenterPresentation NotesJust as important as what is inside the egg is the environment outside the egg. Eggs needs a moist, warm environment in which to survive. They must also be turned to make sure that the chick develops correctly. Mother hens will sit on their eggs to keep them toasty and humid, and they know instinctually when to turn them. We humans don’t have the time or ability to sit on eggs! Instead, we use incubators, and there are many different types of these, to provide the warmth and humidity, and we must remember to turn the eggs at least three times a day to keep the baby chicks inside healthy and happy.

Little cells make big progress:

Day 1• Cells are already specializing• Muscle, nerve, and digestive cells appear• The eyes and blood vessels begin to form

Day 2• Heart and ears form• Heart begins to beat

Note: The different parts of the chick develop at the same time. - Blood and blood vessels - Brain, eyes and digestive system, etc.

PresenterPresentation NotesEven as early as the first few hours, the embryo begins to form specialized cells that will become complex organ systems later on. Muscle cells, nerve cells, and digestive system cells are forming—but none of them will work yet. Blood vessels begin to form, but no blood can pass through the vessels yet. Even the eyes are starting to form! The embryo will be about 3 millimeters long by the end of the first day. Things happen quickly on day two: at 25 hours old, the chick’s heart begins to form; at 33 hours the ears begin to form; and at 42 hours the heart starts to beat and send blood through the vessels that connect the yolk—the source of the chick’s nutrients—to the embryo’s developing organs. Can you see the heart beating in this video? At the same time, other specialized cells continue to divide and grow. Note that the chick develops each of its body systems at the same time. You might think that blood vessels develop first, then the blood that will pass through them forms but this is untrue. Instead, both of these things form at the same time and when both are ready they start to work together. Different organ systems develop at the same time too. For example, even though all organs rely on the brain for instructions, the brain, eyes, digestive system and all other organs form at the same time instead of waiting for one to finish before the other one starts. When they are all ready, they will work together.

Little cells make big progress:

Day 3• Distinguishable head and tail• Leg and wing buds can be seen• Specialized cells begin to form

tongue, liver, kidneys and lungs• More blood vessels

Day 4• Toes begin to form• Mostly present, but tiny• Embryo separates from yolk

PresenterPresentation NotesBy day three, the head and tail can be seen as well as the buds that will become wings and legs. The specialized cells begin to form tissues, which will eventually form organs like the tongue, liver, kidneys, and lungs. To supply all of these cells with the nutrients they need to keep growing, more blood and blood vessels form. On day four the toes begin to form. At this point, most of the chick’s body parts are present, but most of its organs are still too simple to function. The chick is so tiny that it’s heart is only a fraction of an inch from it’s eye. It still has a lot of growing to do! The chick’s tiny body has separated from the yolk. The embryo still relies upon the yolk for nutrients, but now it also rests upon the yolk as if it were a comfy pillow. In this time lapse video of a chick’s development from day 2 to day 3, you can see the heart begin to beat regularly as the chick’s small body lengthens and widens out.

The formative days:

Day 5• Reproductive organs develop• Leg bones form

Day 6• Beak becomes visible• Wing bends at the elbow• Intestines begin to loop

PresenterPresentation NotesOn day five, the chick is already starting to form the next link in the lifecycle chain as it’s reproductive organs begin to form. This means that, before a chick is even hatched from an egg, it is getting ready to make more chicks later on. On day five the leg bones begin to form, but it will still be a few days before any of the chick’s bones harden. On day six, the beak becomes visible and the chick is able to bend its wing at the elbow. Its intestine, which before was just a simple tube, is getting so long that it must loop around in order to fit inside the chick’s body.

The formative days:

Day 7• Feather buds appear• Eye develops rapidly• Knees bend

Day 8• More feather buds appear• Egg tooth forms

PresenterPresentation NotesYou may be asking yourself, well, when will this silly chick get its feathers? Day seven is the day! Today the first feather buds begin to appear along it’s tail and thigh. The eye is developing rapidly in this stage, and today the chick will be able to bend it’s knees for the first time.

Time to get moving:

Day 9• Eyelids and kneecaps develop• Chick moves more• Yolk is noticeably smaller

Day 10• Chick moves even more• Refined features develop

Day 11• More movement• Beak and bones harden

PresenterPresentation NotesIn the next few days the chick will start moving around a lot—it needs to exercise it’s new muscles as much as possible while it can. Pretty soon, the little chick will be too big to move inside the egg at all! On day nine, eyelids and kneecaps develop. The yolk still has plenty of nutrients left to help the chick until it hatches, but the yolk is now noticeable smaller than it was in the beginning. On day ten the chick moves even more and some of it’s more refined features develop: claws, comb, and flight feathers. In the video, you can see that the chick is still exercising by the end of day 11. This exercise is good for it’s skeleton too, and it will begin to use calcium from the shell to harden its bones and beak.

Bigger and stronger:

Day 12• Development continues• Scales appear on legs

Day 13• Bones continue to harden• Wishbone is formed

PresenterPresentation NotesOn day 12, development continues and scales appear on the legs. On day 13, the right and left collar bones fuse together to form the wishbone.

Bigger and stronger:

Day 14• Movement slows• Skull hardens• Yolk is much smaller

Day 15• Scales, claws, and beak become firm• Growth continues• Organ development continues

PresenterPresentation NotesBy day 14, the chick is starting to feel crowded. Today or tomorrow, it will turn its head toward the bottom of the egg and it will stay that direction until it hatches—simply because it is too big to turn around! The skull has begun to harden. The chick has used much of the yolk’s energy and nutrients, and by now the yolk is noticeably smaller and even difficult to distinguish from the rest of the developing chick. On day 15, the scales, claws, and beak become firm as it continues to develop all of its other parts.

The waiting game:

Day 16• Feathers cover the whole body• Development continues (bones

are almost fully hardened)

Day 17• Chick’s beak turns toward air cell

Day 18• More development… almost

ready!

PresenterPresentation NotesBy day 16 everything is in place. Now it is just a matter of time before the chick’s body is developed and strong enough to survive outside the egg. Day 17 brings an exciting development—the chick turns its beak toward the air cell to get ready to take its first breath! Since the chick can’t move inside the egg, it “turns” its head by developing a double bend in its neck. In other words, it’s neck makes a full loop, first toward the skinny side of the egg, then rounding back toward the blunt side of the egg where the air cell is. By day 18, the chick is almost ready. This x-ray video of an 18-day chick shows how the skeleton is nearing full development.

Countdown to hatch:

Day 19• It can breathe!

Day 20• Lungs at 100%

Day 21• Get ready… Today is the day!

PresenterPresentation NotesOn day 19, the chick breaks through the membrane on the air cell and takes its first breath. The lungs inflate and begin to function. The last of the yolk sac enters the chick’s body where any remaining yolk will be used to help the chick survive after it hatches. On day 20, the chick relies completely on its lungs for respiration and its body takes up all the space in the egg. It’s finally day 21, and the chick’s neck begins to spasm automatically… and this is what will cause the chick to peck its way out!

How it hatches:

It’s not easy!• First it must peck shell open• 3-8 hour rest• Turns and pecks around the

inside of the egg (2-5 hours)• Pushes and pushes, until…

It finally breaks free!

PresenterPresentation NotesThe class will probably be able to hear the chick tapping long before the chick’s beak pops through. Once it does, the exhausted chick will take a “breather,” literally breathing the outside air to get used to the new environment and to prepare for the hard work ahead. This break will take 3 to 8 hours. Once the chick has rested, it begins to turn slowly inside the egg, tapping the shell open as it goes and effectively cutting off the top of the egg. Once it has made it about ¾ of the way around (this may take up to 5 hours), things start to go much faster! The chick begins to push and struggle against the top of the egg, trying to break out in a process should take only about 40 minutes. Then suddenly, it’s the moment you’ve been waiting for! The chick emerges, wet and panting for air. It will lie still for a while, but don’t worry—it is just resting. After all, breaking out of an egg shell is hard work! Soon enough, it will begin to rise to its feet. It may seem unsure of itself at first while it figures out its muscle coordination, but within hours it will be all the way dried out and peeping and hopping around under the brooder lights.

After a chick is hatched, it needs:

• Rest!• Warmth and humidity• Food and water• Room to exercise

PresenterPresentation NotesUnlike human babies, chicks emerge with bodies that are able to walk within hours! Chicks rely on their instincts to know when they need to eat, drink, and find warmth. All we humans need to do is provide them with the food, water, and heat as well as some room to exercise, and the chicks will “babysit” themselves.

The End

Brought to you by Utah Agriculture in the Classroom

Special thanks to: Chickscope(http://chickscope.beckman.uiuc.edu/)Ohio UniversityOhio 4H

PresenterPresentation NotesFor more resources and lesson plans on hatching chicks, please visit us online at Utah.Agclassroom.Org.

http://chickscope.beckman.uiuc.edu/

Hatching ScienceA Brief Egg-splanationA Brief Egg-splanationA Brief Egg-splanationDays 1 – 4Days 1 – 4Days 5 – 8Days 5 – 8Days 9 – 11Days 12 – 15Days 12 – 15Days 16 – 18Days 19 – 21Time for the Egg-citement!It’s awful cute, but now what?Hatching Science